Do you need to keep track of your kids? Are you spying on your hubby? Are you monitoring an employee? Spying on someone is not nice. If you are uncomfortable with someone using your computer - lock them out. If you are monitoring your children there are loads of programs. Search google for "child monitoring software"
Jen you need 007 spy installed on that system http://www.e-spy-software.com/ this software will tell you what ever you need to know (Screen shot, Key Logging, Application Launched..etc ) and it runs in promiscuous mode (VERY DISCREET).